The present invention relates generally to optoelectronic devices, and more specifically to parallel optics assemblies for use in fiber optic communications.
The majority of computer and communication networks today rely on copper wiring to transmit data between nodes in the network. However, copper wiring has relatively limited bandwidth for carrying electrical signals which greatly constrains the amounts of data that it can be used to transmit.
Many computer and communication networks, including large parts of the Internet, are now being built using fiber optic cabling which has superior bandwidth capabilities and can be used to transmit much greater amounts of data. With fiber optic cabling, data is transmitted using optical or light signals (also called photonic signals), rather than with electrical signals. However, since computers use electrical signals as opposed to optical signals the light signals used to transmit data over fiber optic links must be translated to electrical signals and vice-versa during the optical communication process. Building such fiber optic networks therefore requires optoelectronic modules which mechanically and optically interface optical transmission mediums such as fiber optic cables to electronic computing and communications devices and transform optical signals to electronic signals and electronic signals to photonic signals. Further, in order to provide the required bandwidth for high-speed communications multiple fiber optic elements must be used in systems often referred to as xe2x80x9cparallel opticsxe2x80x9d systems for concurrently transmitting multiple signals over a single cable. The optoelectronic modules must therefore also be adapted for accommodating cables having multiple fibers which are presented for connection purposes in closely spaced arrays of fiber optic elements supported in special ferrules attached to the ends of the cables.
Signal conversion from electrical to optical and optical to electrical may be provided for through the use of arrays of semiconductor elements (photoactive components) which are deployed on semiconductor or integrated circuit chips (optoelectronic devices). These photoactive components may be devices such as photodiodes which act as photo-receivers or laser diodes which act as photo-transmitters. While modules using such devices can provide satisfactory signal conversion performance, the building of effective parallel optics subassemblies is a challenge. The optical alignment of the photoactive devices with the ends of the thread-like fiber optic elements must be precise for an effective transfer of optical power. Since the fiber optic ends in parallel optics modules are closely spaced the complexity of this alignment task is further increased. Further, the module must be designed to efficiently handle the processing of the electrical signals and to efficiently interface with outside computer and communication systems.
One past alignment technique for use in constructing parallel optics modules was to etch alignment grooves along the surface of a silicon substrate using photolithography techniques. These grooves were then used in precisely positioning the fibers and fiber optic ends in aligned relationships to edge-emitting laser diodes. Although this technique can accurately align the optical components, the arrays must be manually assembled. Consequently, the process is labor intensive and results in low yields due to assembly errors and quality assurance problems.
More recently some parallel optics modules have come to use metal lead frames for mounting the photoactive devices. The lead frames then have alignment holes that cooperate with guide pins for alignment purposes. The guide pins extend from the holes in the lead frame to corresponding holes in a ferrule supporting the optic fibers in order to provide for the alignment of the ferrule with the lead frame and the fibers with the photoactive devices. However, for this design to be effective the optoelectronic device must be very accurately mounted onto the metal lead frame at the same time the alignment holes extending through the lead frame must be very accurately positioned. This alignment is hard to achieve and should the optoelectronic device or alignment holes be inaccurately positioned serious optical misalignment may occur even though the optical fibers may seem to be correctly aligned.
The present invention relates to parallel optics modules for use in fiber optic communications and more particularly to subassemblies for use in transmitting and receiving photonic (light) signals. Parallel optics modules provide for communications between computer and communication systems over fiber optic cables containing multiple fibers for carrying multiple concurrent signals. The subassembly of the present invention is adapted for interfacing between computer or communication systems and the ferrules on the ends of the fiber optic cables which are used to support and present the ends of the fiber optic elements.
The subassembly includes a receptacle, a lens and alignment frame, a carrier assembly and a casing structure for mounting and supporting these components. The carrier assembly includes a carrier frame section which is attached to the lens and alignment frame. An optoelectronic device comprising either an array of photoactive components such as either VCSELS for converting electrical signals to optical signals or PIN diodes for converting optical signals to electrical signals is mounted on the frame section. The lens and alignment frame includes a tower structure having a set of guide pins and an array of lenses precisely positioned with respect to the guide pins. The tower and guide pins are operative for providing accurate mechanical alignment between the lens and alignment frame and the ferrule as the guide pins mate with alignment holes in the ferrules and as the tower is fixed into a window in the inner end of the receptacle which helps position receptacle holding the ferrule with respect to the lens and alignment frame. The lenses are operative for accurately directing photonic signals through the lens and alignment frame between the fiber ends presented by the ferrule and the photoactive components of the optoelectronic device mounted on the carrier frame section. The lens and alignment frame functions to interface the fibers of the ferrule with the photoactive components of the optoelectronic device. The carrier assembly also includes one or more semiconductor chips for use in signal processing, a flex circuit section for a facilitating communications among its components and a small circuit board with an edge connector formed on one of its ends. The edge connecter is used to removably connect the subassembly to a jack which may be mounted on a circuit board in a computer or communications system. The carrier assembly also provides for the processing of the electrical signals and for the connection of the subassembly to a computer or communications system.